replace default grids

I have a section that lost the standard grids lines. If I add lines using "format/borders", the grid lines are different than the default grid lines. How can I replace these grids without deleting the cell themselves?

Try selecting the area where the grid lines are missing.
Right-Click then select: Format cells -> Border
Under Presets click the None box.
Click: OKBorders.JPG
This should reset all the lines leaving just the background grid.
HTH

As Steve said in post #4 fill hides the grid.
If you want borders similar to the grid in a fill area:LtGreyGrid.JPG
Use these settings:NewBorders.JPG
Otherwise, I for one don't know what you are asking. HTH

Although I can't duplicate it now, I have seen this happen that after performing some function, the gridlines disappear leaving you with a block of white area. It has nothing to do with filling the cells with a color, it seems almost random.

If you go to an unused section of the sheet and copy a range of cells then paste over the missing cells by Right click>Paste Options: Formatting, you should get your borders back. Paste Formatting will not paste over your data just the formatting